Preparation of low friability rigid polyurethane foam

ABSTRACT

An improvement is disclosed in the preparation of rigid polyurethane foams which have relatively high surface friability. The improvement resides in the use of a select group of supplemental polyether polyols having 2-3 hydroxy groups in order to reduce the friability of the resulting foam.

' [22] Filed:

United States Patent [191 Alexander PREPARATION OF LOW FRIABILITY v RIGID POLYURETHANE FOAM [75] lnventor: Roy P. Alexander, Killingworth,

Conn.

[73] Assignee: Olin Corporation, New Haven,

Conn.

Sept. 23, 1974 211 App]. No.: 508,544

[52] US. Cl 260/25 AS; 260/25 AM [51] Int. Cl. C08G 18/14; C08G 18/48; C08G 18/50 [58] 1 Field of Search 260/2.5 AS, 2.5 AM

[56] References Cited UNITED STATES PATENTS 3,269,961 8/ 1966 Bruson 26012.5 AP 3,369,014 2/1968 Booth "260/25 AS Dec. 23, 1975 3,419,532 12/1968 Jackson ll7/138.8 D 3,442,888 5/1969 Degginger 260/25 AS 3,630,973 12/1971 Ardis 260/25 AM 3,728,288 4/1973 Cobbs.... 260/2.5 AS 3,741,921 6/1973 Lapkin... 260/25 AS 3,847,844 11/1974 Fuzesc 260/2.5 AS

Primary ExaminerDonald E. Czaja Assistant Examine'F-C. Warren Ivy Attorney, Agent, or Firm-F. A. lskander; T. P. ODay bility of the resulting foam.

17 Claims, No Drawings PREPARATION OF LOW FRIABIIJITY RIGID POLYURETHANE FOAM This invention relates to an improvement in the production of polyurethane foam. More particularly, the invention relates to the reduction of surface friability in rigid polyurethane foams.

It is known in the art that polyether polyols which are derived from 4,4,4-trichloro-l,2-epoxybutane can be 1 used to advantage in the preparation of a highly flame retardant, rigid polyurethane foam. See for example U.S. Pat. Nos. 3,269,961, 3,630,973, and 3,741,921.

However, it has recently been learned that the use of certain such polyols yields a foam which is often plagued with a high degree of surface friability. As such, the foam requires special handling and it cannot be used to advantage, if at all, in those applications in which the foam is sprayed onto, and is required to adhere to, certain surfaces such as in the on-site insulation of homes and industrial structures.

Now an improvement has been found for eliminating or minimizing the surface friability of rigid otherwise friable polyurethane foam. This objective is achieved, according to the invention by including in the foam forming reaction mixture a select group of polyether polyols having 2-3 hydroxy groups and a molecular weight from about 1,000 to about 6,000.

The improvement disclosed herein may be utilized in reducing the friability of any rigid polyurethane foam which is characterized by a relatively high degree of surface friability. However, it is preferred to employ the improvement of the invention in connection with the preparation of those rigid polyurethane foams which are prepared from a reaction mixture comprised of an organic polyisocyanate, a foaming agent, a reaction catalyst and, as the main reactive polyol, an adduct of a polyhydroxy compound and 4,4,4-trichloro-l,2-

. epoxybutane. This adduct, hereinafter referred to as the main polyol reactant, may beprepared by methods well known in the art. For example, it can be prepared by condensing, optionally in the presence of an preparingthe main polyol reactant is that selected from the group consisting of a mixture of dextrose and water,

a mixture of dextrose and an aliphatic diol or triol, and l the specification and claims herein, the term dextrose" is intended to include hydrous dextrose, such as a-d-glucose monohydrates, as well as anhydrous dextrose, e.g., d-glucose. ln accordance with the most preferred embodiments of the invention a mixture of dextrose and an aliphatic diol or triol is used as the initiator.

The 4,4,4-trichloro-l ,Z-epoxybutahe may be used in purified form, as a crude product of the dehydrohalogenation of 4,4,4-trichloro-2-halobutanol, or as a mixture with a non-halogenated alkylene oxide, e.g., ethylene oxide,propylene oxide, butylene oxide and mixtures thereof. Thus the term 4,4,4-trichloro-l ,2-epoxybutane as used in the specification and claims herein includes any such materials and mixtures which are suitable for condensation with a polyhydroxy initiator to form a polyol that is useful in the production of polyurethane foam.

In preparing the main polyol reactant, a wide variety of conventional oxyalkylation catalysts may be employed, if desired, to promote the condensation reaction between the 4,4,4-trichloro-l,2-epoxybutane and the polyhydroxy initiator. However, when a catalyst is used itis preferred to use an acid catalyst such as a Lewis acid, e.g:, boron trifluoride or an etherate derivative thereof. .Usually carried out at a temperature of about 30-200 "C, the condensation reaction is allowed to proceed until. a polyether polyol is obtained which has a hydroxylmumber from about to about 800, preferably about 260-550, and more preferably about 300-450.

Pursuant to the method of the invention, the polyurethane foam is prepared from a reaction mixture comprising a main polyol reactant, as described above, and a select second polyether polyol. This second polyol, the use of which is critical to reducing the friability of the foam according to the invention, is hereinafter referred to as the supplemental polyol.

As indicated above, the supplemental polyol is characterized by a functionability of 2-3, i.e., 2-3 hydroxy groups in the molecule, and a molecular weight of about l,0O0-6,000. In accordance with the conventional method for converting molecular weight to hydroxyl number, this molecular weight range corresponds to a hydroxyl number range of about 1 15-19 in the case of the difunctional supplemental polyols and about 168-28 in the case of the trifunctional supplemental polyols.

As with the main polyol reactant, the supplemental polyol can be prepared by prior art oxxyalkylation techniques. For example it can be prepared by condensing, in the presence of an alkaline catalyst such as KOH, an aliphatic diol, triol or mixture thereof with an alkylene oxide having 2-4 carbon atoms or with a mixture of such oxides using random or stepwise oxyalkylation techniques. Illustrative such oxides are ethylene oxide, propylene oxide and butylene oxide. The aliphatic diols and triols which are used in preparing the supplemental polyol include those mentioned illustratively above in connection with the preparation of the main polyol reactant.

In accordance with a preferred embodiment of the invention, the supplemental polyol is prepared using, as the oxyalkylating agent, propylene oxide alone or followed by, i.e., capped with, ethylene oxide. Pursuant to this embodiment, the supplemental polyol is an oxypropylated or oxypropylated then oxyethylated diol or triol, the triol being most preferred.

In preparing the supplemental polyol, the oxyalkylation reaction is allowed to proceed until the desired molecular weight is reached, at which time the reaction is terminated and the resulting polyol is recovered. As noted above, the molecular weight of the resulting polyol may range from about 1,000 to about 6,000 and preferably from about 1,200 to about 4,500. In accordance with the most preferred embodiments of the invention, a supplemental polyol as described above is used which has a molecular weight of about 2,0004,000.

Any suitable proportion of the supplemental polyol may be employed which is effective in reducing the friability of the foam without otherwise interfering with, or detrimentally altering, its properties. Usually a proportion is used ranging from about to about 35, and preferably about 8-30, parts per every 100 parts by weight of the main polyol reactant. The requisite proportion of the supplemental polyol may be preparatorily blended in with the main polyol reactant or it may be added separately to the foam-forming reaction mixture.

In preparing the foams of the invention, the abovedescribed polyols are reacted with an organic polyisocyanate in the presence of a reaction catalyst and a foaming agent. Either the one-shot method or the prepolymer technique may be employed in carrying out the reaction. Any suitable organic polyisocyanate, or mixture of polyisocyanates, may be employed which is capable of reacting with a polyether polyol to form a polyurethane. Illustrative are toluene diisocyanate, such as the 80:20 and the 65:35 mixtures of the 2,4:2,6- isomers, methylene-bis(4-phenylisocyanate), 3,3'-bitolylene 4,4-diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, naphthylene-l ,5-diisocyanate, hexamethylene diisocyanate, polymethylene polyphenylisocyanate, and the like. The preferred isocyanates are toluene diisocyanate, polymethylene polyphenylisocyanate (which is available as a commercial product, varying in functionability from'2.2 to 3.2, under the trademark PAPI), and mixtures thereof. The amount of isocyanate employed in the preparation of the polyurethane foams should be sufficient to provide at least about 0.9, and preferably about 1.0-1.2, NCO groups per each hydroxy group present in the foam-forming reaction system. A 100 multiple of the ratio of NCO to OH groups in the foam-forming reaction system is referred to as the index.

The foaming agent employed in preparing the polyurethane foams can be any one of those known in the art to be useful for this purpose such as water, the halogenated hydrocarbons, and mixtures thereof. The preferred foaming agents are the halogenated hydrocarbons which include, for example, monofluorotrichloromethane, difluorodichloromethane, the trichlorotrifluoroethanes, dichlorotetrafluoroethane, methylene chloride, chloroform, carbon tetrachloride, and the like. The amount of foaming agent, or mixture of foaming agents, can be varied over a wide range. Generally, however, the halogenated hydrocarbons are employed in an amount ranging from about 1 to about 75 parts by weight per 100 parts of total polyols in the foam-forming reaction system; and generally water is employed in an amount ranging from about 0.1 to about 10 parts by weight per 100 parts of total polyols.

Any of the catalysts, or mixtures thereof, which are known in the art to catalyze the polyurethane foamforming reaction may be employed in preparing the foams of the invention. These include the tertiary amines, such as N-methylmorpholine and triethylene diamine, and the organic metal salts such as stannous octoate and dibutyltin dilaurate. Generally the catalyst is employed in any suitable catalytic proportion such as from about 0.05 to about 3.0, and preferably from about 0.075 to about 2.0, percent by weight based on the total weight of polyols in the reaction system.

It is preferred in the preparation of the polyurethane foams of the invention to employ minor amounts of a conventional polyurethane foam surfactant. Typical of these are the silicon-based surfactants such as the sililcone oils and soaps and the siloxanes. Usually the amount of surfactant ranges up to about 2 parts by weight per parts of total polyols in the reaction system.

Various additives may also be incorporated in the polyurethane foam-forming reaction mixture, if desired, such as fillers, dyes, plasticizers, deodorants, and antioxidants.

The improved process of the invention provides a relatively simple and practically attractive route to resolving the problem of high surface friability in rigid polyurethane foam. Furthermore, this objective is achieved at minimum cost and without undermining or altering the other basic properties of the foam.

The polyurethane foams of the invention are of utility in a variety of commercial and industrial applications including for example the production of foam-insulated food and beverage containers, sporting goods, and like applications. They are of particular utility in those applications requiring a rigid foam which, along with being flame retardant, can be sprayed onto, and adheres to, wood and other structural materials. Such applications include the on-site generation of foam in the insulation of houses arid other structural installations.

The following examples are provided to illustrate the invention. In these examples, a variety of supplemental polyols are used as indicated. Otherwise, the other foam forming ingredients are essentially the same throughout. They are as follows:

lngredients Parts by Weight Main polyol reactant 1000 Trifluorochloromethane foaming agent 46.0

Dimethylcyclohexylamine catalyst 1.0

Dow Corning 193 Surfactant 2- Polymethylene polyphenylisocyanate 1 15 index) This is a 360 hydroxyl numher polyether polyol prepared by condensing, in the presence of boron trifluoride etheratc catalyst. 4.4,4-triehloro-l,Z-epoxyhutane with an equi-molar mixture of ethylene glycol and a-d-glucose monohydrate.

This is a silicone-glycol copolymer described in an August 1968 Dow Corning bulletin No. 05-146.

"' This is a commercial product of the Upjohn Company purchased under the trademark "PAPl and having an approximate functionahility of 2.6.

' The proportion of isocyanate was calculated to provide in each example an index of l 15.

EXAMPLEl I A rigid polyurethane foam, identified as E-l..was prepared from a reaction mixture consisting of the above ingredients, in the indicated proportions, and 20 parts by weight of oxypropylated glycerin, molecular weight 3,000, as a supplemental polyol. The ingredients were handmixed and foamed in a square cardboard box. After being cured, the resulting foam was removed from the box and its surface friability was tested in accordance with the test described above. The foam exhibited very slight surface crumbling and it was given a low friability rating.

EXAMPLES 2-10 Except for one modification, the identical procedure of Example I was used to prepare 9 foams identified as E-2 through E-10. The modification is that instead of the 3,000 molecular weight oxypropylated glycerin which was used in Example 1, other supplemental polyols were used. The identity of each of these supplemental polyols and the surface friability rating of the resulting foams are provided in Table 1 below.

COMPARISON l-5 Except for one modification, the exact procedure of Example 1 was followed in preparing and testing five rigid foams identified as C-l through C-5. The modification was in connection with the use of the supplemental polyol. Thus in carrying out Comparison 1 no supplemental polyol was included in the foam forming formulation; and in Comparisons 2-5 various supplemental polyols were used in lieu of the 3,000 molecular weight oxypropylated glycerin which was used in Example I. These supplemental polyols, all of which do not meet the molecular weight criterion specified according to the invention, are identified in Table 1 along with the surface friability ratings for each of foams C-l through C-S.

Table 1 Surface Foam Supplemental Polyol Used Friability E-l oxypropylated glycerin, mol wt.

3000 Low E-2 Oxypropylated ethylene glycol,

mol. wt. 2000 Low E-3 oxypropylated ethylene glycol,

mol. wt. 3000 Low E-4 oxypropylated ethylene glycol,

mol. wt. 4000 Low E-S Ox ro ylated then oxyethylated (l5 enoiies EO) glycerin, mol.

wt. 5340 Low E-6 oxypropylated then oxyethylated mo es E0) glycerin, mol.

wt. 5840 Low E-7 oxypropylated then oxyethylated (5 moles E0) glycerin, mol.

wt. 3000 Low 58 oxypropylated then oxyethylated (7.5 moles E0) glycerin, mol. E 9 wt. 3000 T d l Low Ox ro ate l cerin, mo wt.

100 8 Py g y Moderate E-lO Ox ro lated cth lene l col,

moii wti i 000 y g y Moderate C-l None High C-2 Diethylene glycol High 03 Oxypropylated ethylene glycol,

mol. wt. 400 High C-4 Oxypropylated ethylene glycol C 5 80]. wt. 7100 d I I High x ro ate cenn. mo

WL OO g y High These polyols were prepared by the sequential nxyalkylntiun of glycerin lirst with Table l-continued Surface Foam Supplemental Polyol Used l-riability propylene oxide and The data in Table 1 demonstrates the reduction of surface friability which obtains by using a variety of supplemental polyols, per Examples 1 through 10, according to the invention, as compared with foam C-l in which no supplemental polyol was used. This data further demonstrates, per C-2 through C-5, that practically no reduction in surface friability is achieved where other supplemental polyols, which do not meet the molecular weight criterion of the invention, are employed at the same level as used in Examples l-lO.

What is claimed is:

1. In a process of preparing a rigid polyurethane foam from a reaction mixture comprised of a p'olyether polyol reactant, an organic polyisocyanate reactant, a reaction catalyst and a foaming agent, said polyether polyol reactant having a hydroxyl number of about 150-800 and being the product of condensing 4,4,4-tric'hloro-l,2-epoxybutane with a mixture selected from the group consisting of a mixture of dextrose and water, a mixture of dextrose and an aliphatic diol or triol, and a mixture of dextrose, water an an aliphatic diol or triol, the improvement of including in said reaction mixture a second polyether polyol having 2-3 hydroxy groups and a molecular weight from about 1,000 to about 6,000, said second polyether polyol being employed in a proportion which is effective in reducing the friability of said foam.

2. A polyurethane foam prepared by the process of claim 1.

3. The process of claim 1 wherein said second polyether polyol is an oxypropylated or oxypropylated than oxyethylated diol or triol.

4. The process of claim 3 wherein said second polyether polyol has a molecular weight of about l,2004,500.

5. A polyurethane foam prepared by the process of claim 4.

6. The process of claim 4 wherein said polyether polyol reactant is the product of condensing, in the presence of a Lewis acid catalyst, 4,4,4-trichloro-l ,2- epoxybutane with a mixture of dextrose and an aliphatic diol or triol alcohol.

7. The process of claim 6 wherein said polyether polyol reactant has a hydroxyl number of about 260-550.

8. A polyurethane foam prepared by the process of claim 7.

9. The process of claim 7 wherein said second polyether polyol has a molecular weight of about 2.0004,000 and is an oxypropylated triol or an oxypropylated then oxyethylated triol.

10. The process of claim 9 wherein said second polyether polyol is employed in a proportion of about 8-30 parts per every parts by weight of said polyether polyol reactant.

11. A polyurethane foam prepared by the process of claim l0.

12. The process of claim 10 wherein said Lewis acid catalyst is boron trifluoride or an etherate derivative thereof.

agent is a halogenated hydrocarbon foaming agent and said organic polyisocyanate is toluene diisocyanate, polymethylene polyphenyl isocyanate, or a mixture thereof.

17. A polyurethane foam prepared by the process of 

1. IN A PROCESS OF RIGID POLYURETHANE FOAM FROM A REACTION MIXTURE COMPRISED OF A POLYETHER POLYOL REACTANT, AN ORGANIC POLYISOCYANATE REACTANT, A REACTION CATALYST AND A FOAMING AGENT, SAID POLYETHER POLYOL REACTION CATALYST AND A DROXYL NUMBER OF ABOUT 150-800 AND BEING THE PRODUCT OF CONDENSING 4,4,4-TRICHLORO-1,2-EPOXYBUTANE WITH A MIXTURE SELECTED FROM THE GROUP CONSISTING OF A MIXTURE OF DEXTROSE AND WATER, A MIXTURE OF DEXTROSE AND AN ALIPHATIC DIOL OR TRIOL, AND A MIXTURE OF DEXTROSE, WATER AN AN ALIPHATIC DIOL OR TIOL, THE IMPROVEMENT OF INCLUDING IN SAID REACTION MIXTURE A SECOND POLYETHER POLYOL HAVING 2-3 HYDROXY GROUPS AND A MOLECULAR WEIGHT FROM ABOUT 1,000 TO ABOUT 6,000, SAID SECOND POLYETHER POLYOL BEING EMPLOYED IN A PROPORTION WHICH IS EFFECTIVE IN REDUCING THE FRIABILITY OF SAID FOAM.
 2. A polyurethane foam prepared by the process of claim
 1. 3. The process of claim 1 wherein said second polyether polyol is an oxypropylated or oxypropylated than oxyethylated diol or triol.
 4. The process of claim 3 wherein said second polyether polyol has a molecular weight of about 1,200-4,500.
 5. A polyurethane foam prepared by the process of claim
 4. 6. The process of claim 4 wherein said polyether polyol reactant is the product of condensing, in the presence of a Lewis acid catalyst, 4,4,4-trichloro-1,2-epoxybutane with a mixture of dextrose and an aliphatic diol or triol alcohol.
 7. The process of claim 6 wherein said polyether polyol reactant has a hydroxyl number of about 260-550.
 8. A polyurethane foam prepared by the process of claim
 7. 9. The process of claim 7 wherein said second polyether polyol has a molecular weight of about 2,000-4,000 and is an oxypropylated triol or an oxypropylated then oxyethylated triol.
 10. The process of claim 9 wherein said second polyether polyol is employed in a proportion of about 8-30 parts per every 100 parts by weight of said polyether polyol reactant.
 11. A polyurethane foam prepared by the process of claim
 10. 12. The process of claim 10 wherein said Lewis acid catalyst is boron trifluoride or an etherate derivative thereof.
 13. The process of claim 12 wherein the mixture used in preparing said polyether polyol reactant is a mixture of Alpha -d-glucose monohydrate and ethylene glycol.
 14. A polyurethane foam prepared by the process of claim
 13. 15. The process of claim 13 wherein said reaction mixture comprises a silicon-based surfactant.
 16. The process of claim 15 wherein said foaming agent is a halogenated hydrocarbon foaming agent and said organic polyisocyanate is toluene diisocyanate, polymethylene polyphenyl isocyanate, or a mixture thereof.
 17. A polyurethane foam prepared by the process of claim
 16. 